Variable condenser



Allg- 1943- G. M. EHLERS EI'AL VARIABLE CONDENSER Filed May 31, 1941 2 Sheets-Sheet l a 13 is 2; z w

INVENTORS az'ofiazwz $172525. 5

GEORGE x. U, M

ATTORNEY Aug. 10, 1943. G. M.. EHLERS .ET AL VARIABLE CONDENSER Filed May 51, '1941 2 Sheets-Sheet 2 P [A a 2i i a \\\\\\\\\\\\\w\mwmmmw bra J! mzm o 55 a fijkmmmum a W W 6 a g 4 w m 1 I Patented Aug. l0, 1943 VARIABLE CONDENSER George M. Ehlers and George Kodama, Milwaukee Wis., assignors to Globe-Union 1110., Milwaukee, Wis, a corporation of Delaware Application May 31, 1941, Serial No. 396,087

4 Claims.

This invention relates to an improvement in variable condensers.

An object of the invention is to provide a condenser wherein the individual conductor elements are of novel construction, are combined in an advantageous and special manner with each other, and are organized in an unique manner with their insulating support and with their dielectric respectively.

A still further object of the invention is to provide a condenser of this character, which is simple, compact, and closely organized in construction, reliable and efficient in operation, which makes available a range of capacities heretofore not obtainable, and which is susceptible to convenient and economical production on a commercial scale.

Other objects and advantages reside in certain novel features of the construction, arrangement, and combination of parts, which will be hereinafter more fully described and particularly pointed out in the appended claims, reference being had to the accompanying drawings forming a part of this specification, and in which:

Figure 1 is a view in central, vertical, longitudinal cross section illustrating a variable condenser constructed in accordance with the present invention;

Figure 1a is a fragmentary, sectional view similar to Figure 1 but showing the insulating stator 30 and rotor and the condenser plates combined therewith on an enlarged scale for the sake of clearness and illustration.

Figure 2 is a perspective view illustrating the fixed plates of the condenser, their insulating 35 disc support and the terminals combined with certain of the plates;

Figure 3 is a group view in perspective showing the rotatable plates of the condenser, the dielectric disc on which they are mounted, the ad- 40 Figure 5 is a perspective view showing the op- 50 posite face of the dielectric disc from that shown in Figure 3;

Figures 6 and 'l are cross sectional views taken on lines 6-6 and 'l-I, respectively, of Figures 4 and 5;

Figure 8 is a diagram illustrating the manner in which the fixed and movable plates of the condenser shown in Figures 1 to 7 are connected in an electrical circuit;

Figure 9 is a view similar to Figure 1 but showing another embodiment of the invention;

Figure 9a is a fragmentary sectional view similar to Figure 9, but illustrating the insulating stator and rotor and their condenser plates on an enlarged scale for the sake of clearness and illustration.

Figure 10 is a perspective view showing the fixed condenser plates, their insulating support, and the terminal combined with one of the plates, in the form of the invention shown in Figure 9;

Figure 11 is a perspective view, illustrating the rotary condenser plates and the dielectric disc on which they are mounted when the construction takes the form illustrated in Figure 9;

Figure 12 is a view similar to Figure 10 but showing the opposite side of the insulating disc from that shown in Figure 10;

Figure 13 is a perspective view further illustrating the dielectric disc shown in Figure 11, the view being from the opposite side from that shown in Figure 11; and

Figure 14 is a diagram showing how the condenser plates shown in Figures 8 and 13 are connected in an electrical circuit.

Referring to the drawings, and more particularly to Figures 1 to 8, inclusive, it will be seen that in the form of the invention illustrated in the views mentioned, the condenser comprises an insulating support or stator I preferably in the form of the disc of moulded insulating material, such as a. moulded ceramic having appropriate insulating properties. To one face of the disc I the fixed plates of the condenser, designated at 2, 3, 4, and 5, are applied. The plates 2, 3, 4, and 5 may be applied as metallic films, coatings, or platings, painted or sprayed on the face of the insulating disc. Usually silver salts are applied and then reduced either chemically or by heat. Where the condenser plates are constituted as a silver film they may be copper-plated, if desired. Terminals 6 and l are applied to the face of the insulating disc I opposite that which carries the condenser plates 2, 3, 4, and 5, and they are electrically connected to the condenser plates 2 and 4 by means of suitable metal eyelets or rivets 8 and 9. The eyelets 8 and 9 are countersunk in the metallic films constituting the condenser plates 2 and 4 and hence leave the outer surfaces of the condenser plates smooth and plane. The terminals 6 and l facilitate the connection of the plates 2 and 4 in an electrical circuit, and as illustrated in Figure 8 they connect the plates 2 and 4 to the same'side of an electrical circuit which is indicated for the purpose of simplicity in description as the positive side of the circuit so'that the plates 2 and 4 are of thesame polarity. The plates 2, 3, 4 and 5 are approximately segmental'in form and more specifically take the approximate dimensions of a quadrant although their radial edges as well as their inner portions are spaced from each other so that the plates themselves are electrically insulated from each other.

To mount the insulating disc or stator I on I a suitable support, as for example on the chassis I4 of a mounting panel or bracket I5 which may be insulating material. As shown in Figure 1, the body of the bushing extends through the opening I 4. A washer I6 is interposed between the flange I2 oi the bushing and the margin of the opening I4 on one side of the panel i5. On the opposite side of the panel I5 a nut I1. is threaded on the' bushing I3 and has clamping engagement with the panel I5 so as to coact with the flange I2 and washer I8 to fixedly support the bushing I3 on the panel I5.

A metallic adjusting shaft I8 is rotatabl fitted in the bearing bushing I3. The outer end of this shaft has an adjusting knob I9 releasably secured thereto to facilitate turning of the shaft. A oring or snap ring is snapped into an annular groove provided on the periphery of the shaft I8 and bears against the outer end of the bushing I3 to limit the extent to which the shaft I8 may move axially through the bushing in a direction toward the right, as viewed in Figure 1. The inner end of the shaft projects beyond the flanged end. I2 of the bushing I3 and is combined with a dielectric disc or rotor 2| in a manner which will hereinafter be more fully described.

The dielectric disc or rotor 2| may be conveniently and advantageously constituted of moulded and firedceramic material of high dielectric con- Stant or of other suitable insulating material.

While the material of which the dielectric disc or rotor 2| i formed may be of various suitable compositions, it is preferably composed of titanium dioxide and rare earth. For example, it may be any one of the compositions disclosed in the application of George M. Ehlers and R olland R. Roup, filed August 25, 1938, Serial No. 226,734, for .Electric capacitators and dielectric for the same, whichapplication is assigned to the assignee of the present application. The dielectric disc or rotor 2| is formed with a central aperture 22 and with a flanged or thickened rim portion 23. The movable plates of the condenser, designated at 24, 25, 26 and 21, are applied, preferably as metallic films, platings or coatings, to the outside face of the dielectric disc or rotor 2 I, and are for the most part located within the confines of the rim 23 thereof. These movable conlenser plates 24, 25, 26, and 21 are similar in form, as well as in structure, to the fixed condenser plates 2, 3, 4, and 5 of the stator, and like ,driving and conducting arm 30.

have their radial edges, as Well as their inner portions, spaced from each other to an extent suflicient to electrically insulate the plates 24, 25, 26, and 21 from each other.

The shaft I8 has a reduced portion 28 which extends through and beyond the central aperture 22 of the dielectric disc 2|. portion 28 of the shaft is surrounded by an insulating collar or washer 29. The reduced por tlon 28 of the shaft also extends through a central opening provided, therefor in a combined The extreme outer end of the reduced portion 28 of the shaft is riveted or staked over, as-at 3|, so as to be rigidly connected to the central portion of the arm 30.; The arm 38 is of spring or resilient metal of good electric conductivity, such as spring steel, and its outer ends are adapted to be received or fitted in diametrically'opposite notches 32 formed in the rim 23 of the dielectric disc or rotor 2| thereby rotatably coupling or establishing a driving connection between the adjusting shaft I8 and the dielectric disc or rotor 2 I. The parts are so dimensioned and proportioned that the driving arm 30, which is initially slightly bowed, must be flexed and placed under tension when its ends are seated in the notches and the O- ring 20 is snapped into its groove, so that these parts perform the 'further function of pressing the smooth inner face of the dielectric disc firmly against the smooth faces or surfaces of the fixed plates 2, 3, 4, and 5 of the condenser. The'arm 30 is also made to perform the additional function of electrically connecting the plates 25 and 21 in electric circuit, and for this purpose the condenser plates-25 and 21 have their films or coatings formed with extensions 33 and 34 which cover the floors of the notches 32 and have good electrical contact with the end of the arm 30 fitted in said notches. As illustrated in Figure 8. the shaft |8, and consequently the arm 30, are at ground potentialthat is, they may be regarded as connected to the negative side of the circuit in which the condenser is incorporated. The arm 38 is however spaced and consequently electrically insulated from the condenser plates 24 and 26.

Provision is made for connecting the plates 24 and 26 to the positive side of the electrical circuit, and to accomplish this in a simple and advantageous way. For this purpose the fixed condenser plates 2 and 4 are formed with armate connecting or collectingstrips 35 and 36 which curve or are about the aperture I0 of the insulating disc I in the manner illustrated in Figure 2. The movable condenser plates 24 and 26 have extensions 31 and 31' which extend radially to the aperture 22, then axially across the inner peripheral wall of this aperture 22, and then around the margin of the opening and on the inner'face of the dielectric disc 2| to form contact'shoes 38 and 39 of the form shown in Figure 5. In the assembly the contact shoes 38 and 39 have wiping contact with the collector or conductor strips 35 and 36 so that a positive potential is impressed on the condenser plates 24 and 26 as well as on the fixed condenser plates 2 and 4. The fixed condenser plates 3 and 5 are connected up to the negative side of the electrical circuit, and this may be conveniently accomplished by extending the film constituting the plates 3 and 5 across the outer edge of the disc I and then radially across the opposite face thereof, to form conducting arms ,40

them are approximately of segmental form, but and 4| which continue down and merge into a This reduced keying projections 40 and 4| which are embedded in the material of the disc I. The covering 42 for thefloor of the socket II has good electrical contact with the flanged end I2 of the bearing bushing l3, and since the shaft I8 is a working fit in the bushing It, the condenser plates 3 and 5 are also at ground potential or may be regarded as connected to the negative side of the electrical circuit.

In this construction, when the knob 19 is adjusted to cause the shaft to so move the disclike rotor 2| as to bring its plates 24, 25, 28, and 21 into opposed relationship with the plates 2, 3, 4, and 5. respectively, the capacitance of the condenser is at its minimum since plates of the same polarityare opposed to each other. The maximum capacity of the condenser may be had by so turning the knob l9, shaft I8, and rotor 7 2| as to bring the plates 24, 25, 26, and 21 of the rotor into opposed relationships with the plates 3, 4, 5, and 5, respectively, since in such an adjustment plates of opposite polarity have their full areas in opposed relationship. Intermediate adjustments of the rotor 2| with respect to the stator I provide for a wide range of intermediate capacity variations.

The form of the invention shown in Figures 9 to 14 inclusive is in all broad and substantial respects the same as that shown in Figures 1 to 8, the difference being in the fact that the stator and the rotor each are provided with two condenser plates of opposite polarity rather than four. In the construction shown in Figures 9 to 14, the stator I and rotor 2| are provided as before. The stator is mounted on the supporting panel l5 by bushing l3, washer l6, and nut I! as before. The rotor 2! is adjusted by the shaft 18 which is equipped with a knob I9, the inner end of the shaft being reduced and provided with the insulating washer 29 and also being staked as at 3| to a coupling and conducting arm 30.

As shown in Figure 10, the stator I has two condenser plates, designated at 50 and 5|, the condenser plates being substantially of semicircular form or segmental form, rather than quadrant or sector shape, as in the other embodiment. Theplates 50 and 5| are metallic films, platings or coatings of the same character as the plates of the other form of the invention, and have their edges spaced slightly so as to be electrically insulated from each other and yet just as in the other embodiment the plates 50 and 5| are otherwise substantially coextensive with the entire surface of the stator to which they are applied. The terminal 52, like the terminal 6, is connected by a rivet 53 to the plate 5|, as in the other embodiment of the invention, and provides a convenient means for connecting the plate 5| to one side of an external circuit, as for example to the positive side of the external circuit, as indicated diagrammatically in Figure 14. The plate 50 has its film extended across the edge of the disc-like stator l and down to the outside face thereof to provide a conducting arm 54 corresponding to the conducting arm 40 and in electrical connection with the bushing I3, as in the other embodiment, so that the condenser plate 50 is at ground potential, or, as illustrated diagrammatically in Figure 14, is connected to the negative side of the power source. The disclike rotor 20 of dielectric material is in this form of the invention the same as inthe other except that instead of having four movable condenser plates it has two semi-circular or segmental condenser plates, designated at 55 and '56, the ad- Jacent edges of these plates being slightly spaced from each other so that the plates are electrically insulated from each other. Only one of the movable condenser plates, namely the plate 55, has an extension 55 covering the floor of one of the notches 32 since only one of themovable condenser plates is to be connected to the negative side of the power source. The outer peripheral edge of the other condenser plate 56 lies entirely within the confines of the rim 23 of the rotor. The arm 30 serves to place the plate 55 at ground potential, as before. The movable condenser plate 56 has an extension from its inner periphery which goes across the inner peripheral wall of the aperture 22 of the rotor and is formed into a contact shoe 5] on the ,inner face of the disc-like dielectric rotor, and is arranged and adapted to have wiping contact with an arcuate conducting or collecting strip 58 formed as an integral extension of the fixed condenser plate 5|, the shoe 51 and strip 58. serving to impress a charge of the same polarity on the plate 56 as that impressed on plate 5|. In this instance, as before, the maximum value of the condenser capacity is realized by bringing the movable plates of the rotor into opposed re-- lationship with the fixed plates of the stator of opposite polarity, whereas minimum capacity is realized by rotating movable plates of the rotor into opposed relation with the fixed plates of the stator of the same polarity.

While we have shown and described several constructions in which the invention may be advantageously embodied, it is to be understood that the constructions shown have been selected merely for the purpose of illustration or example, and that various changes in the size, shape, and arrangement of the parts may be made without departing from the spirit of the invention or the scope of the subloined claims.

We claim:

1. A variable condenser of the character described comprising a disc-like stator of insulating material, a disc-like 'rotor of dielectric ma,- terial in face-to-face engagement with said stator, a pair of fixed condenser plates applied as metallic films to the face of the stator engaged with the face of the rotor, a pair of similar movable condenser plates applied as metallic films to the outside face of the rotor, a terminal carried by the stator and in electrical contact with one of its plates for connecting said plate in an external circuit, a collector strip provided adjacent the center of the stator as an extension of the plate to which the terminal is connected, a contact shoe carried by the rotor having wiping contact with said strip and electrically connected to one of the plates of the rotor, a metallic bearing bushing carried by said stator, a connecting arm between the bushing and the other condenser plate of the stator, a rotary adlusting shaft supported in said bearing bushing,

, and a metallic driving arm fastened to the shaft tent to which the positively and negatively charged plates overlap.

2. A condenser of the character described comprising a disc-like stator of insulating material, a disc-like rotor of dielectric material concentrically disposed with respect to the stator and supported for rotation about the common axis of the stator and rotor and in face-to-face relation therewith, a plurality of fixed condenser plates applied as metallic films to angularly spaced portions of the face of the stator engaged with the face of the rotor, a plurality of similar movable condenser plates applied as metallic films to angularly spaced portions of the outside face of the rotor, terminals carried by the stator and in electrical connection with alternate condenser plates thereof for connecting such plates to the positive side of an external electrical circuit, cooperable contact strips and contact shoes carried respectively by said positively charged plates of the stator and corresponding alternate plates of the rotor whereby said alternate plates of the rotor are also impressed with .positive charges, a metallic bearing bushing carried by the stator, a metallic shaft rotatably fitted in and in electrical connection with said bushing, said shaft and said bushing being at ground potential, means connecting the bushing with condenser plates of the stator intermediate alternate positively charged plates thereof, and a combined driving and conducting arm interconnecting the shaft and the rotor to rotatively couple the rotor to the shaft and electrically connect the plates hereof inermediate its positively charged alternate plates to the negative side of the circuit.

3. A condenser of the character described comprising a metallic bearing bushing, a disc-like stator of insulating material supported on said bushing, a metallic adjusting shaft rotatably supported in said bushing, said shaft and said bushing being at ground potential, a rotor of dielectric material fixed to and rotatable with said shaft, condenser plates applied as metallic films to the rotor and stator, means for connecting certain of the condenser plates of the stator in an external circuit so as to impress a positive charge thereon, means for transferring the potential impressed on said plates of the stator to plates of the rotor, and means for connecting plates of the rotor and stator to thenegative side of the circuit and including connections from the last mentioned stator plates to the bushing and from the last mentioned rotorplates to the shaft.

4. A condenser of the character described comprising a bearing bushing, a disc-like stator of insulating material supported on said bushing and having a central opening aligned with the opening of the bushing, an adjusting shaft rotatably supported in said bushing and projecting beyond the same, a disc-like rotor of dielectric material disposed in face-to-face engagement with the stator and having a central opening through which said shaft projects, condenser plates applied to the face of the stator engaged with the face of the rotor and to the outside face of the rotor, means for limiting the extent to which the shaft may move axially in the bushing in the direction toward the rotor, and a resilient metallic driving arm fastened to the inner end of the shaft and having its ends pressing against the rotor to press the rotor against the stator, said ends also having driving engagement-with the rotor whereby when the shaft is turned the rotor is adjusted relative to the 

